The present invention relates to a TAB (Tape Automated Bonding) tape with a stiffener, which is a combined cooling plate and stiffener being a so-called xe2x80x9cstiffenerxe2x80x9d, and a tape BGA (Ball Grid Array) semiconductor device using the same.
A one-metal TAB tape is usual as a TAB tape, and such one-metal TAB tape is prepared by forming a wired pattern on either surface of an insulating film made of polyimide resin used for a tape base material.
In this respect, there is a tendency to direct high frequency in chips mounted on a personal computer and the like, whereby a need for a circuit having a high transmission rate increases. With increase in data transmission rate, a new problem of noise generation due to electromagnetic field coupling between leads appears on a fine-pitch wiring in a TAB tape, and it became impossible to ignore such problem. For instance, there is such a problem that a ringing (resonance) phenomenon arises between leads disposed with a spacing of 30 xcexcm, so that a signal wave form of clock pulse deforms remarkably.
In order to overcome such problem as described above, the following constitution is considered effective. Namely, the constitution is arranged in such that a ground layer is disposed on the surface opposite to a side of a tape base material on which a wired pattern has been formed, whereby influence of noise due to mutual inductance between wirings due to use of leads in a package does not result in a problem in view of operating characteristics.
In these circumstances, a two-metal (double layered) TAB tape wherein a wired pattern has been formed on opposite surfaces of a polyimide resin insulating film used for a tape base material, respectively, is noticed as a TAB tape capable of eliminating such problem as described above.
A semiconductor device having a conventional T-BGA (Tape BGA) structure wherein the two-metal TAB tape is used is shown in FIG. 5.
First, a circuit pattern 21 with a signal circuit containing solder ball pad sections 26, a bonding pad section 27, and a routed lead section is formed on either surface of a tape base material 1 composed of a polyimide resin insulating film. Then, a part of the circuit pattern 21 is insulated with an insulating film 2 made from a photo solder resist (PSR). A ground layer 6 is disposed on the other surface of the tape base material 1. The above-described solder ball pad sections 26 and the bonding pad section 27 are electrically connected to the ground layer 6 through a conductive via section 3, whereby a two-metal TAB tape 50 is constituted. The resulting two-metal TAB tape 50 is bonded to a stiffener 40 wherein a concave portion 41 for mounting a semiconductor chip has been defined on a central portion of a metal sheet through an adhesive 5 to obtain a TAB tape with a stiffener.
Then, a semiconductor chip 7 is bonded to the concave portion 41 of the above-described stiffener 40 with the use of a device-fixing agent 9 as its adhesive. An electrode 71 of the semiconductor chip 7 is connected with the above-described circuit pattern 21 by a bonding wire 8, and further the above-described semiconductor chip 7 and the bonding wire 8 are sealed by means of a sealing resin 100, whereby the semiconductor device is constituted. Solder balls 4 are installed on the respective solder ball pad sections 26.
According to the above-described constitution, there is the ground layer 6 being an electrically conductive layer beneath the tape base material 1 being a thin insulating layer. Accordingly, eddy currents flow in the ground layer 6 along directions wherein magnetic fluxes produced by electric currents flowing through respective wirings are cancelled in the case when a high frequency signal is loaded on the wirings in the signal circuit. As a result, an apparent inductance and an apparent inductive crosstalk can be reduced, whereby reliability and speeding up in a velocity of propagation of electrical signals are achieved.
However, two-metal and one-base material TAB tape is very expensive, so that a T-BGA semiconductor device prepared by using such TAB tape becomes very expensive, consequently.
Accordingly, an object of the present invention is to provide an inexpensive TAB tape with a stiffener wherein a two-metal and two-base material TAB tape having a structure prepared by bonding an ordinary single metal TAB to a tape material of a ground layer is used for solving the above-described problems and improving electrical characteristics thereof, and as a result, equivalent reliability and equivalent speeding up in a velocity of propagation of electrical signals to those of the case where a conventional two-metal and one-base material TAB tape is employed are achieved as well as to provide a T-BGA semiconductor using such TAB tape with a stiffener as described above.
In order to achieve the above-described object, the present inventions have been constituted as described hereinafter.
(1) A TAB tape with a stiffener according to a first invention as claimed in claim 1 is characterized by that a circuit pattern containing a signal circuit is formed on either surface of a first tape base material made from an insulating film; a part of the circuit pattern is covered with an insulating film; a via hole penetrating the first tape base material is defined on a connecting regional section used for a via, which is one of connection regions required for electrical connections and is not covered with the insulating film to constitute a one-metal TAB tape; the one-metal TAB tape is bonded to a tape for second metal prepared by providing a metallic film layer on either surface of a second tape base material made from an insulating film through an adhesive layer on which an opening corresponding to the via hole has been defined in such that the metallic foil layer of the tape for second metal is positioned on the opposite surface of the first tape base material; an exposed portion for wire bonding, which has not been covered with the one-metal TAB tape, is allowed to remain on the metallic foil layer in case of the bonding operation; and a stiffener made from a metallic sheet being bonded onto a side of the tape for second metal of a two-metal and two-base material TAB tape prepared by the above-described bonding operation through an adhesive.
According to such TAB tape with a stiffener as described above, a two-metal and two-base material TAB tape having a structure wherein a one-metal TAB tape, which is easily manufactured, is bonded to a tape used for a second metal prepared by providing a metallic foil layer on either surface of a second tape base material made from an insulating film through an adhesive layer, on which an opening corresponding to the above-described via hole has been defined, in such that the metallic foil layer of the above-described tape for second metal is positioned on the other surface of the above-described first tape base material has been used. Thus, it can be very inexpensively manufactured as compared with the case where a conventional two-metal TAB tape is employed.
Furthermore, this TAB tape with a stiffener has such structure wherein a connecting regional section used for a via being a part of a circuit pattern is disposed on either surface of a first tape base material, while a part of a metallic foil layer made of, for example, copper foil is disposed on the other surface thereof, and a blind via hole that extends from the connecting regional section for via to reach the metallic foil layer through a via hole in the first tape base material and an opening in an adhesive layer is defined. Hence, when the connecting regional section for via on the upper edge of the hole is electrically connected with a part of the metallic foil layer on the bottom of the hole in the blind via hole, a potential of the metallic foil layer can drop to a ground potential.
As a manner for attaining an electrical connection in the blind via, there are, for example, the following three manners wherein the first one is a method for melting a solder ball to a mount the same in the above-described blind via, the second one is a method for connecting electrically a connecting regional section for via on the upper edge of the via hole with a part of the metallic foil layer on the bottom of the hole in the blind via by means of a bonding wire, and the third one is a method for folding a connecting lead section extending on the above-described via hole as a part of a circuit pattern, and subjecting the connecting lead section thus folded to contact bonding or welding with respect to a part of the metallic foil layer on the bottom of hole.
In this respect, it is preferred that Au/Ni plating has been applied to a part (with which an electrical connection is to be made) or the whole of the above-described metallic foil layer.
(2) A TAB tape with a stiffener according to a second invention of claim 2 as claimed in claim 1 is characterized by that a connecting regional section for via on the upper edge of a blind via hole is electrically connected with a part of the metallic foil layer on the bottom of the hole by means of a conducting means in the blind via hole extending from the connecting regional section for via in the above-described one-metal TAB tape through the via hole of the above-described first tape base material and the opening in the above-descried adhesive layer to reach the metallic foil layer in the above-described tape for second metal.
(3) A TAB tape with a stiffener according to a third invention of claim 3 as claimed in claim 1 or 2 is characterized by that a part of the above-described blind via hole is sealed with a resin so as to cover the conducting means and the connecting regional section for via.
(4) A semiconductor device according to a fourth invention as claimed in claim 4 is characterized by that an insulating film having a metallic foil layer is bonded onto a portion immediately below a one-metal TAB tape, which has a circuit pattern on either surface thereof and a via hole has been bored on a part thereof by means of punching processing or the like processing through an adhesive layer on a part of which an opening corresponding to the above-described via hole has been defined likewise; a stiffener is bonded to the one-metal TAB tape thus prepared through an adhesive; a semiconductor device is mounted on the stiffener; a solder ball is molten to mount in a blind via hole composed of the above-described via hole and the above-described opening, whereby a specific potential is given to the above-described metallic foil layer situated immediately below the one-metal TAB tape; further, a partial region in the metallic foil layer on a side near to the semiconductor device is exposed from a boundary of the one-metal TAB tape; and the part thus exposed is connected with an electrode of the semiconductor device by means of a bonding wire.
According to such semiconductor device as described above since a TAB tape with a stiffener prepared from a two-metal and two-base material TAB tape having a structure wherein a one-metal TAB tape, which is easily manufactured, is bonded to a tape used for a second metal through an adhesive layer has been used, it can be vary inexpensively manufactured as compared with the case where a conventional two-metal and one-base material TAB tape is employed.
Furthermore, the present invention provides such a constitution wherein a specific electrical potential is applied to a metallic foil layer situated beneath a one-metal TAB tape by melting a solder ball to mount the same in a blind via hole composed of a via hole and an opening. Accordingly, generation of noise due to electromagnetic field coupling between leads in a circuit pattern on either surface of the one-metal TAB tape can be suppressed, so that reliability and speeding up of a velocity of propagation in electric signal can be achieved.
Besides, the present invention provides such a constitution wherein a sectional region (a metallic foil layer section) on the side near to a semiconductor device in the metallic foil layer is exposed outside a region of a one-metal TAB tape, the section thus exposed is connected with an electrode of the semiconductor device by means of wire bonding. As a result, a ground line of the semiconductor device can lead to a ground potential through the above-described metallic foil layer and a blind via hole. Accordingly, speeding up of a transmission rate and stabilization of operation characteristics can be achieved in this point of view.
In this respect, it is preferred that Au/Ni plating has been applied to a part (with which an electrical connection is to be made) or the whole of the above-described metallic foil layer.
(5) A semiconductor device according to a fifth invention as claimed in claim 4 is characterized by that a connecting regional section for via capable of wire bonding is formed around the upper edge of the above-described via hole; the connecting regional section is connected with a part of the metallic foil layer (copper foil) on the bottom in the hole by means of a bonding wire; and the section thus connected is further covered with a resin in stead of melting a solder ball to mount in the above-described blind via hole.
According to the characteristic feature described above, since an electrical connection between the connecting regional section for via and a part of the metallic foil layer on the bottom of the hole in the blind via hole may be carried out as a part of a wire bonding step for connecting a device electrode with a circuit pattern through such wire bonding. Further, the connected section is covered with a resin, so that sufficient protection can be achieved.
(6) A semiconductor device according to a sixth invention as claimed in claim 4 is a characterized by that a connecting lead section is allowed to extend on the above-described via hole as a part of the above-described circuit pattern; the connecting lead section is folded; and the connecting lead section thus folded is fixed to a part of the metallic foil layer on the bottom of the above-described hole by means of contact bonding or welding in stead of melting a solder ball to mount in the above-described blind via hole.
According to the characteristic feature as described above, there is provided a constitution wherein an electrical connection between the connecting regional section and a part of the metallic foil layer on the bottom of the hole is made in such that a connecting lead section, which extends as a part of a circuit pattern 21, is provided on a via hole in the form of, for example, a flying lead, the connecting lead section thus obtained is folded into an S-shape by means of a bonding tool, and it is fixed to a portion of a metallic foil layer on the bottom of the hole by means of contact bonding or welding. As a result, there is no need to implement two-points bonding, but it is sufficient to provide only one bonding portion on a side of the metallic foil layer.